Using Events

The Application class of the Console component allows you to optionally hook
into the lifecycle of a console application via events. Instead of reinventing
the wheel, it uses the Symfony EventDispatcher component to do the work:

Typical Purposes: Doing something before any command is run (like logging
which command is going to be executed), or displaying something about the event
to be executed.

Just before executing any command, the ConsoleEvents::COMMAND event is
dispatched. Listeners receive a
ConsoleCommandEvent event:

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useSymfony\Component\Console\Event\ConsoleCommandEvent;useSymfony\Component\Console\ConsoleEvents;$dispatcher->addListener(ConsoleEvents::COMMAND,function(ConsoleCommandEvent$event){// get the input instance$input=$event->getInput();// get the output instance$output=$event->getOutput();// get the command to be executed$command=$event->getCommand();// write something about the command$output->writeln(sprintf('Before running command <info>%s</info>',$command->getName()));// get the application$application=$command->getApplication();});

Using the
disableCommand()
method, you can disable a command inside a listener. The application
will then not execute the command, but instead will return the code 113
(defined in ConsoleCommandEvent::RETURN_CODE_DISABLED). This code is one
of the reserved exit codes for console commands that conform with the
C/C++ standard.:

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useSymfony\Component\Console\Event\ConsoleCommandEvent;useSymfony\Component\Console\ConsoleEvents;$dispatcher->addListener(ConsoleEvents::COMMAND,function(ConsoleCommandEvent$event){// get the command to be executed$command=$event->getCommand();// ... check if the command can be executed// disable the command, this will result in the command being skipped// and code 113 being returned from the Application$event->disableCommand();// it is possible to enable the command in a later listenerif(!$event->commandShouldRun()){$event->enableCommand();}});

Typical Purposes: Handle exceptions thrown during the execution of a
command.

Whenever an exception is thrown by a command, the ConsoleEvents::EXCEPTION
event is dispatched. A listener can wrap or change the exception or do
anything useful before the exception is thrown by the application.

useSymfony\Component\Console\Event\ConsoleExceptionEvent;useSymfony\Component\Console\ConsoleEvents;$dispatcher->addListener(ConsoleEvents::EXCEPTION,function(ConsoleExceptionEvent$event){$output=$event->getOutput();$command=$event->getCommand();$output->writeln(sprintf('Oops, exception thrown while running command <info>%s</info>',$command->getName()));// get the current exit code (the exception code or the exit code set by a ConsoleEvents::TERMINATE event)$exitCode=$event->getExitCode();// change the exception to another one$event->setException(new\LogicException('Caught exception',$exitCode,$event->getException()));});

Typical Purposes: To perform some cleanup actions after the command has
been executed.

After the command has been executed, the ConsoleEvents::TERMINATE event is
dispatched. It can be used to do any actions that need to be executed for all
commands or to cleanup what you initiated in a ConsoleEvents::COMMAND
listener (like sending logs, closing a database connection, sending emails,
...). A listener might also change the exit code.

useSymfony\Component\Console\Event\ConsoleTerminateEvent;useSymfony\Component\Console\ConsoleEvents;$dispatcher->addListener(ConsoleEvents::TERMINATE,function(ConsoleTerminateEvent$event){// get the output$output=$event->getOutput();// get the command that has been executed$command=$event->getCommand();// display something$output->writeln(sprintf('After running command <info>%s</info>',$command->getName()));// change the exit code$event->setExitCode(128);});

Tip

This event is also dispatched when an exception is thrown by the command.
It is then dispatched just after the ConsoleEvents::EXCEPTION event.
The exit code received in this case is the exception code.